General purpose household cleaning compositions (GPC's) for hard surfaces such as metal, glass, ceramic, plastic and linoleum surfaces are commercially available in both powdered and liquid form. Powdered cleaning compositions consist mainly of builder or buffering salts such as phosphates, carbonates, silicates etc. Such compositions display good inorganic soil removal, but they can be deficient in cleaning ability on organic soils such as the calcium and/or magnesium salts of fatty acids and fatty/greasy soils typically found in the domestic environment. Such compositions are generally buffered at an alkaline pH by the builder, and as it is generally believed that alkaline pH facilitates the detergency of free fatty acids by conversion into the corresponding soap.
Liquid cleaning compositions generally comprise an organic solvent and have the great advantage that they can be applied to hard surfaces in neat or concentrated form so that a relatively high level of surfactant material and organic solvent is directly delivered onto the soil. These liquid compositions are of utility in the cleaning of hard surfaces such as floors and walls and kitchen or bathroom surfaces as mentioned above and in cleaning soft furnishings such as upholstery, carpets, curtains etc.
Typically, the surfactants used in commercial general purpose cleaners include one or both of linear alkyl benzene sulphonates and secondary alkane sulphonates (SAS).
The incorporation of certain surfactants into such solvent/water compositions presents no difficulties when these surfactants are present at relatively low concentrations. European Patent EP 0344847 (P&G) discloses compositions comprising butoxy-propanol solvents in combination with up to 5% wt sodium linear C8-C18 alkyl benzene sulphonate.
Mixtures of linear alkyl benzene sulphonates with alcohol ethoxylates and optionally small amounts of fatty soaps comprise the surfactant system used in a number of successful, alkaline, commercial products.
A further outstanding technical problem with such compositions is that the surfactants most commonly used, are less biodegradable and consequently less preferable environmentally than other surfactant systems.
In particular, primary alcohol sulphate (hereinafter referred to as PAS) is an environmentally desirable anionic surfactant, both due to its ease of biodegradability as compared with linear alkyl benzene sulphonates and secondary alkane sulphonates and the fact that it can be derived from natural materials such as coconut and other vegetable oils as a source of fatty acid residues.
Primary alcohol sulphate comprises a mixture of materials of the general formulation: EQU RO--SO.sub.3 X
wherein R is a C.sub.8 to C.sub.8 primary alkyl group and X is a solubilising cation. Known counter ions include sodium, magnesium, potassium, ammonium, TEA and mixtures thereof.
GB 1524441 discloses formulations comprising 0-25% magnesium PAS, 0-6% of the magnesium salt of an ethoxylated PAS, dimethyl-dodecylamine oxide and triethanolamine.
EP 125711 (Clarke: 1984) relates to thick, opaque GPC's containing nonionic, anionic (examples are Mg-PAS) and a partially esterified resin.
GB-2160887 (Bristol Myers: 1984) relates to GPC's which comprise solvent, anionics including alkali metal, magnesium, ammonium and TEA-PAS salts and 0.005-3.0% of a nonionic including 75-100% on nonionic of a water insoluble nonionic. The sodium salt of the lauryl sulphate (Na-C.sub.12 PAS) is the most preferred anionic surfactant.
GB 2144763 (P&G: 1983) relates to acidic cleaning composition in the form of a microemulsion, comprising at least 5% solvent and a magnesium salt. The preferred compositions comprise mixtures of nonionic surfactants, paraffin sulphonates, alkyl sulphates (PAS), ethoxylated phenols and ethoxylated alcohols.
EP 0107946 (P&G: 1982) relates to liquid detergent (dishwashing) compositions comprising 6-18% Mg-PAS, together with a water soluble C.sub.13 -C.sub.18 alkane or alkene sulphonate and a water soluble alkyl ether sulphate.
Many of the compositions described in the abovementioned documents comprise added electrolytes, which are believed to enhance cleaning. An outstanding technical problem which stems from the use of added electrolyte is the formation of residues on drying of the composition.